BMI Calculator
Calculate your Body Mass Index and understand your weight category
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Understanding Body Mass Index (BMI)
What is BMI?
Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared. A BMI of 25.0 or more is overweight, while the healthy range is 18.5 to 24.9. BMI applies to most adults 18-65 years.
Why is BMI Important?
BMI is an inexpensive and easy screening method for weight category—underweight, healthy weight, overweight, and obesity. BMI does not measure body fat directly, but research has shown that BMI is moderately correlated with more direct measures of body fat obtained from skinfold thickness measurements, bioelectrical impedance, densitometry (underwater weighing), dual energy x-ray absorptiometry (DXA) and other methods.
Limitations of BMI: Why It’s Not Perfect
While BMI is a useful population-level screening tool, it has several critical limitations for individuals:
- Muscle vs. Fat: Muscle is much denser than fat. A bodybuilder might have a BMI of 30 (classified as obese) while having very low body fat.
- Fat Distribution: BMI doesn't tell you where your fat is stored. "Abdominal fat" (visceral fat) is a much higher health risk than fat stored elsewhere.
- Bone Density: Some people naturally have heavier bones, which can slightly inflate their BMI without indicating excess fat.
- Age and Sex: Women naturally tend to have more body fat than men at the same BMI. Similarly, older adults often lose muscle, which can make a "normal" BMI misleading.
Frequently Asked Questions
Is BMI accurate for children and teens?
No, this calculator is for adults 18 and older. For children and adolescents, BMI is calculated the same way but interpreted differently using age and sex-specific percentiles.
What is a "Normal" BMI range?
According to the World Health Organization (WHO), a normal BMI range is between 18.5 and 24.9. Below 18.5 is considered underweight, and above 25 is considered overweight.
Can I have a high BMI and still be healthy?
Yes, especially if you have high muscle mass. Conversely, you can have a "Normal" BMI and still have high body fat (sometimes called "skinny fat"), which carries its own health risks.
How often should I check my BMI?
For most people, checking once every few months is sufficient. Focus more on long-term trends and overall lifestyle habits rather than daily or weekly fluctuations in weight.
Understanding Body Mass Index (BMI)
What is BMI?
Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared. A BMI of 25.0 or more is overweight, while the healthy range is 18.5 to 24.9. BMI applies to most adults 18-65 years.
Why is BMI Important?
BMI is an inexpensive and easy screening method for weight category—underweight, healthy weight, overweight, and obesity. BMI does not measure body fat directly, but research has shown that BMI is moderately correlated with more direct measures of body fat obtained from skinfold thickness measurements, bioelectrical impedance, densitometry (underwater weighing), dual energy x-ray absorptiometry (DXA) and other methods.
Limitations of BMI: Why It’s Not Perfect
While BMI is a useful population-level screening tool, it has several critical limitations for individuals:
- Muscle vs. Fat: Muscle is much denser than fat. A bodybuilder might have a BMI of 30 (classified as obese) while having very low body fat.
- Fat Distribution: BMI doesn't tell you where your fat is stored. "Abdominal fat" (visceral fat) is a much higher health risk than fat stored elsewhere.
- Bone Density: Some people naturally have heavier bones, which can slightly inflate their BMI without indicating excess fat.
- Age and Sex: Women naturally tend to have more body fat than men at the same BMI. Similarly, older adults often lose muscle, which can make a "normal" BMI misleading.
Frequently Asked Questions
Is BMI accurate for children and teens?
No, this calculator is for adults 18 and older. For children and adolescents, BMI is calculated the same way but interpreted differently using age and sex-specific percentiles.
What is a "Normal" BMI range?
According to the World Health Organization (WHO), a normal BMI range is between 18.5 and 24.9. Below 18.5 is considered underweight, and above 25 is considered overweight.
Can I have a high BMI and still be healthy?
Yes, especially if you have high muscle mass. Conversely, you can have a "Normal" BMI and still have high body fat (sometimes called "skinny fat"), which carries its own health risks.
How often should I check my BMI?
For most people, checking once every few months is sufficient. Focus more on long-term trends and overall lifestyle habits rather than daily or weekly fluctuations in weight.